A conventional apparatus for concentrating and diluting only a specific gas from a gas containing plural gas species includes an ozone concentrating apparatus, a NOx or Freon removing apparatus, a CO2 removing apparatus and the like. In the techniques of the conventional apparatuses, only a specific gas is cooled and is once liquefied or adsorbed on an absorbent, such as silica gel, and in the next step, the gas substance having been liquefied or adsorbed on the adsorbent is again gasified through evaporation or desorption by heating, whereby the specific gas is concentrated. A gas having been concentrated by using the apparatus is utilized as a chemical reactive gas for an apparatus for producing a semiconductor, whereby it is applied to a production technique of a semiconductor having higher quality, and is applied to an environmental improvement technique, such as detoxification of a concentrated toxic gas through heat or catalytic reaction.
A first example of a conventional apparatus for concentrating and diluting a specific gas is such an apparatus that about 10% (220 g/Nm3) of an ozonized gas (oxygen:90%, ozone:10%) generated with an ozone generator is fed to a chamber cooled to from 80 K (−193° C.) to 100 K (−173° C.) to liquefy only an ozone gas, in the next step the gas part in the chamber is vacuumized with an evacuating device, in the further next step the liquefied ozone gas is heated to a temperature around from 128 K (−145° C.) to 133 K (−140° C.) with a heating means, such as a heater, to convert the vacuumized gas part to a 100% ozone gas at from 50 Torr (53 hPa) to 70 Torr (100 hPa), which corresponds to the vapor pressure of ozone, and the vaporized ozone is retrieved (as described, for example, in Patent Document 1).
A second example of a conventional apparatus for concentrating and diluting a specific gas is such an apparatus that an ozonized gas generated with an ozone generator is fed to a chamber having filled therein an adsorbent and having been cooled to a low temperature (−60° C.) to adsorb only an ozone gas to the adsorbent (adsorbing step), and in the next step the gas part in the chamber is evacuated to vacuum with an evacuating device, in the further next step the ozone gas adsorbed to the adsorbent is heated to a temperature around 0° C. with a heating means, such as a heater, whereby a 95% concentrated ozone gas at about 100 Torr (53 hPa) is retrieved from the vacuumized adsorbent part at a flow rate of about 500 cc/min (desorbing step) (as described, for example, in Patent Document 2).
In Patent Document 2, in order to retrieve the concentrated ozone gas continuously, the adsorbing step and the desorbing step are repeated alternately in time series by providing three of the aforementioned chamber having filled therein the adsorbent, and an ozonized gas having a high concentration can be fed stably by providing a buffer tank. It is also disclosed therein that an oxygen gas and the like are fed to the buffer tank along with the concentrated ozone gas, whereby an ozonized gas having an ozone concentration of from 30 to 95% can be fed.
In the field of production of semiconductors, there is severe competition in development for realizing a highly integrated semiconductor device, and for example, there is such a proposal that in a production process of a nonvolatile semiconductor memory device (nonvolatile memory) having a silicon oxide film formed on a nitride film on a silicon wafer, a control electrode and a floating gate electrode are formed in such a manner that an extremely thin oxide film of about 2 nm is formed, and as an oxide film forming means capable of suppressing an interlayer leakage electric current, a low temperature oxidation chemical reaction with a superhigh purity ozonized gas containing no impurity than oxide and ozone gas having 20% (440 g/Nm3) or more and irradiation of an ultraviolet ray or plasma discharge is used to form an oxide film having good quality, whereby such an oxide film can be realized that satisfies the aforementioned thickness and the requirement in electric current regulation (as described, for example, in Patent Document 3).
In the field of production of semiconductors, it is important to form an oxide film having high quality for increasing the integration degree. Accordingly, importance is given to a technique of continuously supplying a superhigh purity ozonized gas of 20% (440 g/Nm3) or more, i.e., a highly concentrated ozone gas, economically in large quantity with safety. The application field of a conventional apparatus for concentrating and diluting a specific gas includes an apparatus for removing a NOx gas or a Freon gas and an apparatus for removing a CO2 gas. The apparatus for removing a NOx gas includes plural steps, i.e., in the first step a Freon gas or a CO2 gas, a gas containing a NOx gas or a CO2 gas is adsorbed to an adsorbent at a low temperature or under pressure, in the second step the gas is desorbed at a high temperature or in a depressurized state, and then in the third step the desorbed NOx, Freon or CO2 gas is decomposed and removed through heat, chemical reaction or catalytic chemical reaction.
As an example of the conventional apparatus for removing a NOx gas, there is proposed that a NOx gas derived from a combustion waste gas is adsorbed to a metallic oxide substance by making the gas in contact with the metallic oxide substance, whereby the NOx gas contained in the combustion waste gas is removed (apparatus for diluting a NOx gas) (as described, for example, in Patent Document 4). The application field of a conventional apparatus for concentrating and diluting a specific gas includes an apparatus for removing a CO2 gas. As the apparatus for removing a CO2 gas, such apparatuses are proposed that a waste gas containing a carbon dioxide gas is adsorbed to porous tubes to remove a CO2 gas from the waste gas (as described, for example, in Patent Document 5), and air in a room containing a carbon dioxide gas is made in contact with a carbon dioxide gas adsorbing sheet with a fan to adsorb a carbon dioxide gas to the carbon dioxide gas adsorbing sheet, whereby the air in the room is cleaned (apparatus for diluting a CO2 gas) (as described, for example, in Patent Document 6). The NOx or CO2 gas thus adsorbed with the apparatus for removing a NOx or CO2 gas contributes to enhancement of efficiency for a processing technique such as reducing into an N2 gas and converting into ammonia, carbon or methane due to activating the surface of the metallic oxide substance and then accelerating the catalytic chemical reaction on the surface of the metallic oxide substance by applying heat or generating discharge, on the surface of the metallic oxide substance.    Patent Document 1: JP-A-2001-133141    Patent Document 2: JP-A-11-335102    Patent Document 3: JP-A-2005-347679    Patent Document 4: JP-A-6-15174    Patent Document 5: JP-A-2000-262837    Patent Document 6: JP-A-11-244652    Patent Document 7: JP-A-2004-359537            (Japanese Patent No. 3,642,572)            Patent Document 8: JP-A-9-208202    Non-patent Document 1: “Ozone wo chushintoshita Kodo Josuii Shori Gijutsu” (Advanced Water Cleaning Technique centering on Ozone), p. 48-49, published by Sanshu Shobo (July 17, Heisei 2 (1990)
It is believed that the invention is not disclosed in the aforementioned conventional art documents and has novelty and inventive step. In particular, such an apparatus is not disclosed that is constituted with a chamber having filled therein a particle material for condensation and vaporization, and a chamber having formed therein a gas transmission member (membrane). Furthermore, no document discloses such an apparatus and method that the upper part of the chamber is cooled with a cooler to condense selectively a specific gas on the surface of the particle material, and other gases than the specific gas are selectively transmitted through the gas transmission member (membrane), and the condensed gas is vaporized on the surface of the heated particle material or gas transmission member (membrane) on the lower part of the chamber, whereby the specific gas is concentrated.
In the conventional technique of concentrating an ozonized gas as a specific gas, in the first step an ozone gas generated with an ozone generator is liquefied or adsorbed to an adsorbent by cooling, in the second step gasses that cannot be adsorbed are evacuated to vacuum, and in the third step the liquefied or adsorbed gas is heated to obtain 100% ozone or a highly concentrated ozone gas of 95%. In the concentrating apparatus, the system becomes complicated since the operations of the three steps are repeated alternately, and control in pressure and flow rate and control of valves for switching the pipings for every steps become complicated, whereby such a problem arises that the apparatus is increased in size, and the cost of the apparatus is increased.
Impurity gases contained in an ozone gas generated with an ozone generator are accumulated as an impurity liquid in a liquefaction container through the liquefying and adsorbing steps of ozone, whereby there is a necessity of removing the impurity liquid periodically, or the impurity liquid remains as being adsorbed to the adsorbent to be a factor of deterioration in performance of ozone adsorption.
Upon vaporizing the liquefied ozone liquid or adsorbed ozone by heating, if they are rapidly heated, abrupt vaporization or desorption occurs from the ozone liquid or adsorbed ozone to cause danger of explosion due to rapid increase of the gas pressure.
Accordingly, since the rapid vaporization or desorption is prevented from occurring, and the vaporization or desorption is to be effected in a low pressure state, there is such a problem that only an ozonized gas having a low pressure can be supplied, and there are such problems that in the field of production of semiconductors, mass production (batch process) cannot be attained, and a concentrated ozone gas cannot be dispersed uniformly to a wafer processing chamber. Furthermore, an ozone gas generated with an ozone generator is continuously fed to a liquefaction chamber or an adsorption chamber to liquefy the gas to a prescribed amount or to adsorb once the gas the adsorbent to around 100% ozone, and the gas that cannot be liquefied or the ozone gas that cannot be adsorbed is discarded to a waste ozone apparatus, which brings about such a problem that an ozone gas cannot be effectively concentrated.
In the conventional technique of removing a NOx or CO2 gas as a specific gas to clean a waste gas or air in a room (dilution of a specific gas), when the adsorption amount of the adsorbent is saturated, such a problem arises that the adsorbent is necessarily regenerated or replaced.
Furthermore, in the case where the NOx or CO2 gas as a specific gas is processed with the processing such as reducing into an N2 gas and converting into ammonia, carbon or methane, due to activating the surface of the metallic oxide substance and then accelerating the catalytic chemical reaction on a surface of a metallic oxide substance by applying heat or generating discharge, on the surface of the metallic oxide substance, there is such a problem that the gas cannot be efficiently processed.